Biofouling is a detrimental type of fouling experienced in industrial water treatment applications. Regardless of industry, water treatment experts spend a considerable amount of their time focused on preventing biofouling of heat exchangers and cooling towers. When biofouled, poorly performing heat exchangers and cooling towers can lead to millions of dollars in lost revenues.
The use of oxidizing and non-oxidizing biocides for microbiological control in industrial applications is known. However, the known chemistries have significant drawbacks when it comes to overall efficacy, safety, and delivery.
Methods for combining stabilizers with oxidizing biocides vary, but include: (i) direct injection of the stabilizer into a biocide such as hypochlorite, which is then injected into an aqueous system, (ii) injection of the stabilizing component and biocide such as hypochlorite into the aqueous system separately but in close proximity, and (iii) creating a solid form of a stabilized product, which is then dissolved into an aqueous system.
Whether stabilized or not, oxidizing biocides have difficulty penetrating biofilms once they have been established. While it is possible to feed an exorbitant amount of oxidizing biocide to essentially “burn” the system, the high levels of free oxidant increase corrosion rates throughout the water system. To help improve the oxidizing biocide's ability to penetrate these films and make contact with the microorganisms, biosurfactants have been implemented.
Biosurfactants, sometimes referred to as biodispersants, significantly improve the efficacy of both oxidizing and non-oxidizing biocides. There are subtle differences between biosurfactants and biodispersants, but they have the same function—minimize the growth and adherence of biofilms. Biosurfactants work by actually removing the biofilm in a scrubbing type action, while biodispersants disperse bio matter so that it cannot agglomerate.
Research has shown that biofilms are typically 30 to 40% organic matter, with the rest being inorganic material such as silt, metals, and other particulate matter. Other dispersants, such as sulfonated polymers and copolymers, are sometimes used in conjunction with biodispersants and biosurfactants to help disperse these inorganic materials. While this approach can be effective, it involves a comprehensive and cumbersome water chemistry program.
Conventional efforts have attempted to address these issues by combining stabilizer, surfactant, and a halide ion in a solid form. However, practical application of the solid form in water systems requires special feed systems such as pot feeders and requires manual handling of the chemicals. Other programs have been developed that generate stabilized oxidizing biocides. For example, researchers have combined a stabilizer and a bromine source into a single chemistry, as well as combined a bromine and surfactant into a single chemistry. But these programs require expensive generators, and may pose significant hazards if the systems fail.